A system-on-a-chip (SOC) refers to integrating various components of a computer or other electronic system into a single integrated circuit, or chip. An example SOC may contain a central processing unit (CPU) as well as one or more service devices depending on the intended function and use of the SOC. For example, SOC service devices may include, but are not limited to: a memory storage device, e.g., a double data rate (DDR) dynamic random access memory (DRAM) memory unit; a computer networking interface device, e.g., a Gigabit Ethernet unit; a local device interface that supports connectivity to local input/output devices, e.g., a keyboard, mouse, printer; an extended system bus interface, e.g., a Peripheral Component Interconnect (PCI) or PCI Express bus; and a high-speed input/out interface, e.g., FireWire or Universal Serial bus (USB).
A system-on-a-chip may include a configurable high-performance system backbone bus, or crossbar bus, that allocates connectivity between the CPU and the respective SOC service devices as a shared resource. A crossbar bus typically includes an arbiter module that communicates with the CPU and SOC service devices via a predetermined signal interface to receive requests for bus access. Access to the bus may be based on a set of predetermined rules and priorities. Once a bus access request is allowed between two SOC components, the arbiter module may establish physical connectivity between the devices identified in the bus access request by controlling one or more multiplexers to establish electrical signal connectivity between the respective devices. A system-on-a-chip may include service modules and protocol modules, for example for data transfer, that are part of units whose operation may not be optimal.